Declaring Multiple Variables in JavaScript

Question

In JavaScript, it is possible to declare multiple variables like this:

var variable1 = "Hello World!";
var variable2 = "Testing...";
var variable3 = 42;

...or like this:

var variable1 = "Hello World!",
    variable2 = "Testing...",
    variable3 = 42;

Is one method better/faster than the other?

Answer 1

It's just a matter of personal preference. There is no difference between these two ways, other than a few bytes saved with the second form if you strip out the white space.

Answer 2

Besides maintainability, the first way eliminates possibility of accident global variables creation:

(function () {
var variable1 = "Hello World!" // semicolon is missed out accidently
var variable2 = "Testing..."; // still a local variable
var variable3 = 42;
}());

While the second way is less forgiving:

(function () {
var variable1 = "Hello World!" // comma is missed out accidently
    variable2 = "Testing...", // becomes a global variable
    variable3 = 42; // a global variable as well
}());

Answer 3

var variable1 = "Hello World!";
var variable2 = "Testing...";
var variable3 = 42;

is more readable than:

var variable1 = "Hello World!",
    variable2 = "Testing...",
    variable3 = 42;

But they do the same thing.

Answer 4

It's common to use one var statement per scope for organization. The way all "scopes" follow a similar pattern making the code more readable. Additionally, the engine "hoists" them all to the top anyway. So keeping your declarations together mimics what will actually happen more closely.